The present invention relates to electrostatic precipitators and, more particularly, to a tubular discharge electrode and discharge electrode assembly for electrostatic precipitators which by design has inherent structural integrity and develops an improved electrostatic field profile.
In the operation of an electrostatic precipitator, a gas laden with entrained particulate material is passed through an electrostatic field established about a discharge electrode disposed between two grounded collecting electrodes. The suspended particles become electrically charged as they pass through the electrostatic field and move to, under the electrostatic field, and deposit upon the grounded collecting electrodes flanking the discharge electrode. Each collecting electrode is typically formed of one or more elongated plates disposed and suspended from the top of the precipitator housing in a vertical plane. A plurality of such collecting electrodes are disposed transversely across the precipitator casing in spaced vertical planes parallel to the direction of gas flow through the precipitator.
In the most common electrostatic precipitators, referred to as rigid frame electrostatic precipitators, a box-like framework comprised of a plurality of discharge electrode frames mounted in a framework which is suspended from insulators at the top of the precipitator housing to provide a row of vertically disposed discharge electrodes between adjacent collecting electrodes across the width of the precipitator. The voltage is applied to the discharge electrodes to generate the electrostatic field. Each discharge electrode frame is comprised of a plurality of individual flexible discharge electrode wires tautly strung across the support frame.
As electrode wires are installed at ambient temperatures but operated at temperatures in the range of 150 C. to 250 C., the discharge electrode wires may elongate due to thermal expansion and therefore become loose. Discharge electrode wires may also become loose due to handling during erection and shipment of the discharge electrode frames. Although a loose wire will not impede the dust collection process per se, a loose discharge electrode wire may not clean as well in the rapping process.
Furthermore, flexible discharge electrode wires are structurally weak and may break under the tensioning required to keep them taut and repeated fatigue of rapping and thermal cycling. If a discharge electrode wire does break, it may be moved by the gas flow into contact with the collecting electrode causing shorting of the precipitator and necessitating removal of the precipitator from service.